After just two puffs patients felt less anxious and after ten puffs they were less stressed.

Lead author Carrie Cuttler, assistant professor of psychology at Washington State, said: "Existing research on the effects of cannabis on depression, anxiety and stress are very rare and have almost exclusively been done with orally administered THC pills in a laboratory.

"What is unique about our study is that we looked at actual inhaled cannabis by medical marijuana patients who were using it in the comfort of their own homes as opposed to a laboratory.

"A lot of consumers seem to be under the false assumption that more THC is always better.

"Our study shows that CBD is also a very important ingredient in cannabis and may augment some of the positive effects of THC."

To test how the chemicals in marijuana could help mental health problems Cuttler and her team used data from the app Strainprint, which allows medical marijuana users to track how different doses affects their wellbeing.

One of the main ingredients in medical marijuana, cannabidiol, has also been found to be effective in treating epilepsy and sleep problems

Users rate the symptoms they are experiencing from one to ten before using cannabis, then rate them again 20 minutes after smoking along with how many puffs they had.

"This is, to my knowledge, one of the first scientific studies to provide guidance on the strains and quantities of cannabis people should be seeking out for reducing stress, anxiety and depression," Cuttler said.

"Currently, medical and recreational cannabis users rely on the advice of bud tenders whose recommendations are based off of anecdotal not scientific evidence."

One of the main ingredients in medical marijuana, cannabidiol, is also used in cannabis oil to treat a range of issues including mental health, sleep problems, low appetite, epilepsy, Alzheimer's and palliative care.

It is also said to help prevent the signs of ageing and protect against eczema and psoriasis.

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